The present invention relates, in general, to an electro-mechanical device for controlling the winding off speed of a reel having material thereon, and more particularly, to an electro-mechanical device controlling the winding off speed of a beam, forming part of a loom, and having yarns wound thereon, a control being effected by a combination of the tensiometric detection of the tension in the wound off yarn and an electronic A.C. speed change gear for an induction motor deriving the beam.
The present Inventor is the patentee of a Italian Pat. No. 929,025 disclosing an electronic A.C. speed change gear for induction motors, and the present invention is directed to a successful combination of a tensiometric control device and a speed change gear such as disclosed in Italian Pat. No. 929,025.
Warp let-off devices are used extensively in the fabric weaving industry to ensure the warp, or a plurality of individual thread lengths, extending from a feeding roller or beam to the take-up mechanism of the loom and to weaving devices of the loom, being maintained at substantially constant tension and feeding speed. If abrupt changes in tension occur, or if the feeding speed of the feed roller or beam changes from that of the take-up rollers, there is the possibility of either a thread breakage, due to an increased tension, or a thread tangling due to a decreased tension.
There are known devices which associate portions of the mechanism rotating the warp-carrying beam and the take-up roller driving mechanism, for the purpose of assuring a synchronous operation of one with the other. The interrelation of the two driving mechanisms maintains a feeding rate, of the warp wound off the beam or feeding roller, which is equal to the take-up speed of the warp on the take-up rollers. The tension on the warp can be determined manually or automatically.
In devices used to maintain warp tension, usually termed "variators", it is known to use asynchronous single phase motors having an infinitely variable output speed. Such motors are geared to the variators connected to the feed or beam and to the take-up roller driving mechanism, and afford a more variable speed adjustment than is possible with single speed motors, when the latter are used. Such an asynchronous single phase motor is used in the present invention as well as in the speed change gear forming the subject matter of Italian Pat. No. 929,025.